In a fabrication process of a semiconductor device such as a transistor, when source/drain regions for a MOSFET, an emitter diffusion layer for a bipolar transistor and so on are formed, for example, ion implantation for accelerating and implanting ions such as P, As and B into a semiconductor substrate, a polysilicon layer or an amorphous silicon film has heretofore been utilized as a means for accurately controlling doping level of the dopant, depth of a region to be doped and the like. Recently, in order to meet a demand for miniaturization of semiconductor devices, the dopant concentration and thickness of a region formed by the ion implantation need to be controlled even more precisely.
For example, it is known that, when silicon atoms are scattered out of the normal sites thereof by dopant ions implanted into a single crystalline layer, an amorphous region is formed by these recoil silicon atoms. As a means for measuring the thickness and the like of such an amorphous region formed by these recoil silicon ions, Rutherford backscattering spectrometry (RBS) and the photograph of a cross section taken with a transmission electron microscope (TEM) are conventionally adopted.
Ion implant energy and dose of dopant ions implanted into a silicon substrate are conventionally estimated by 4-terminal sheet resistance measurement or thermal wave method. Similarly, the uniformity of the dopant concentration of an ion implanted layer formed on a silicon substrate in a silicon wafer by the ion implantation is also estimated by 4-terminal sheet resistance measurement or thermal wave method.
On the other hand, ellipsometry, obtaining information such as complex refractive index and thickness by making linearly-polarized light incident on the surface of a substrate at a tilt angle and measuring an elliptical shape of elliptically-polarized light reflected from the substrate surface, is known as a simple optical evaluation method.